, head malformation due to early suture fusion, can result from shunting too much CSF

peritoneum can stop absorbing fluid and form walled-off collection of CSF in belly(usually due to infection)

NOTE:

It is important to distinguish between communicating and non-communicating by CT before doing a lumbar puncture, since a non-communicating obstructive hydrocephalus has Ý pressure above the brain. By draining CSF from the lumbar puncture, you would ß the pressure below the brain and could potentially cause herniation of the brain.

(2) Ex Vacuo

 not enough brain to fill up the space, either from atrophy or maldevelopment